Compressible materials, such as fibers and the like, are often bundled or baled for handling and storage. One example where the material to be compressed and bundled (or baled) is cotton. The cotton (referred to as lint) is compressed in a press or baler to form a bundle or bale. In a known operation, the bale is secured by multiple straps or wires to maintain the bale configuration and stability, and then the bale is wrapped for protection, for example, in a wrap or bag, to protect the cotton from exposure to the environs, dirt, debris or factors that can affect the quality of the baled material, whether it is cotton or any other compressed and baled material. Such wrapping or bag materials are typically made of polyethylene, polypropylene, cotton and the like.
In order to increase the efficiency of the baling and bagging operation, automated systems have come in to use. One such system is disclosed in Nyckowski, et al., published US patent applications, Publication Nos. 2013/0305662 and 2014/0158560, the disclosures of which are incorporated herein in their entirety. In the systems disclosed in the Nyckowski publications, bales of compressible material, such as cotton, are compressed to form bales and inserted directly into a bag in an automated system without the use of straps or wires.
The bales tend to expand after they are compressed. As such, issues may arise with respect to the strength of the bag materials used to contain the bales. One system contemplates using bags made of polymeric materials that are sufficiently strong to contain the compressed bales and to prevent or limit expansion. One high-strength bag is formed from polyethylene terephthalate (PET) tapes that are woven together or loomed to form an elongated tube. The tube can then be folded to form lengthwise gussets and cut to size for individual bags. One end of the tube is sealed, as by stitching to form the bag, leaving the other end open for receiving the compressed bale. Following baling and bagging, the bales are discharged from the system and the open end of the bags are folded and sealed.
Present sealing methods include stitching, stapling, and the use of cable-ties or zip-ties. However, each of these methods has its drawbacks. For example, stitching is a labor intensive operation. An operator must secure the bag and use a stitching or other device to stitch along the entirety or nearly the entirety of the opening. It may also require moving or manipulating the bagged bale in order to access the open area or sealing area. Such an operation requires special equipment and extensive labor operations to seal the bagged bale. In addition, stitching necessarily results in perforations of the bag along the stitch line, which can allow contaminants to enter the bag and can become a weakened point on the bag.
Stapling likewise has its drawbacks. It too requires special equipment, i.e., an industrial stapler and consumables, staples. As with stitching, it is a labor intensive operation that may require moving or manipulating the bales in order to access the seal area. In addition, staples may come loose from a bale and can enter the material, which can contaminate the material or may come loose and jam within the system or otherwise cause problems with the baling or sealing operation. And, stapling can be inconsistent. That is, one bale may be stapled properly, while another may not, which can result in contamination of a bale, or a bag opening and the contents escaping from the bag. Moreover, like stitching, stapling by necessity perforates the bag which can allow contaminants to enter the bag and can create a weakened region of the bag. Another drawback is that staples can result in debris in the plant area around the bagging and sealing operation.
Cable- or zip-ties are also known to be used to seal bags. However, these are labor intensive and require that larger holes be made in bags to insert the ties through bag creating opportunities for contaminant ingress and weakened regions in the bag. In addition, like staples, portions of the ties may come loose from a bale and contaminate the material contained within the bag or jam within the system or otherwise cause problems with the baling or sealing operation. A further drawback is that cable and zip-ties can result in debris in the plant area around the bagging and sealing operation.
Heat sealing is another known method to seal bags, generally. However, the operating characteristics of any heat sealing technique are dependent upon the materials being heat sealed, as well as the material contained within the bag. Employing heat sealing to seal a PET bag being used to contain certain materials, such as cotton, has certain drawbacks due to the high melting point needed to properly form a seal in PET materials. The sealing temperature needed for PET bags is greater than about 450° F. This temperature is too high for use in many compressible materials applications, such as cotton, which has an ignition temperature of about 500° F. Since the melting point of PET is close to the ignition temperature of cotton, using a heat seal to seal bags made of PET that are being used to contain cotton bales may not be feasible.
There is therefore a need for an improved sealing system for bags used to contain highly compressible material, such as cotton, without straps or wires. Desirably, such as system uses heat sealing to seal bags containing the material. More desirably still, such a method can use a lower heating temperature so as to avoid nearing the ignition temperature of materials in the bag, such as cotton. Still more desirably, such a system can use shorter heating times to increase throughput and to reduce the labor required to form the seal.